Loaded telephone-circuits



G. A. KELSALL.

LOADED TELEPHONE cmculs.

.l APPLICATION FILED AUG. IG, 19H. 1,360,757, PantedNov. 30,1920.

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AIIII WN lll/ll U/v/T Y UNITED STATES PATENT OFFICE.

GEORGE A. KELSALL, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A VCORPORATION 0F NEW YORK.

LOADED TELEPHONE-CIRCUITS.

Specication of Letters Patent. Patentgd NOV. 30, 1920' Application filed August 16, 1917. Serial No. 186,487.

To ZZ 11i/0m vit may concern.'

lie it known that I, GEORGE A. lxicLsALL, a citizen of the United States, residing at .Jersey City, in the county of Hudson and State of New Jersey, have invented certain new and useful Improvements in Loaded T elephone-Circuits, of which the following isl a full, clear, concise, and exact description.

This invention relates to loaded telephone circuits, and more particularly to a system of loading, wherein a plurality of physical or side circuits and a plurality of derived phantom circuits are loaded by means of a unitary inductive device.

The object of this invention is to provide a system of loaded telephone circuits wherein a larger number of circuits maybe loaded at a given point by means of a single inductive or loading device than hashitherto been possible. Another object 'of this invention is the provision of such a system which will allow of the independent working of all of the circuits, both physical and phantom, without excessive electrical inagnetic interference or cross-talk between them.

In the systems heretofore known the maximum number of circuits which it was possible to load at a given point by means of a single unitary inductive device or a loading unit was two physical or side .circuits and one derived phantom circuit. By the present invention as many as siX side circuits and 4three derived phantom circuits may be loaded at a given point by means of a single unitary inductive or loading device.

This improvement is accomplished by the use of a twelve-limbed magnetic structure or core having a single winding upon each limb. The limbs may be so located as to form the edges of a cube or they may con- 'form to the arcs of great circles of a sphere or they may be of any other convenient form. The windings on diagonally opposite limbs may forni the line windings ior'the physical or4 'side circuits, while the four windings on generally parallel limbs may be grouped together to make up one derived phantom circuit.

The invention will be more clearly understood b v reference to the drawings wherein:

between the several circuits in accordance with this invention.

Referring to Fig. 1, the .loading device therein shown consists of a branched magnetic structure having twelve limbs numbered 1 to 12 inclusive. This magnetic structure may be composed of any suitable magnetic material; for example, the limbs may conveniently be formed of finely divided iron, the individual particles of which are coated with a thin insulating film, the core members being molded by high pressure, in the manner vdescribed and claimed in a copending application of J. B. Speed, Serial No. 89,409, iiled April 6, 1916, now Patent No. 1,274,952, dated Aug. 6, 1918, and assigned to the saine assignee as the present application.

single winding adapted to be connected into a line conductor of a telephone circuit may be placed on each limb. Windings 13 and 14, located on limbs 1 and 2 respectively, may constitute the line windings of one physical circuit; while windings 15 and 16, located respectively on limbs 3 and 4 may :torm the line windings of a second physical circuit. These four windings may then be grouped together to form a derived phantom circuit. Such a phantom circuit, together with the corresponding physical circuits from which it is derived, will be called for convenience a loading unit, and this particular unit will be designated as loading unit X. Similarly, windings 17 to 20 inclusive, located on limbs 5 to 8 inclusive, may constitute a loading unit which will be designated as loading unit Y. Finally, line windings 21 to 24 inclusive, located on limbs 9 to 12, inclusive, may make up a third loading unit which will be designated as loading unit Z. The line windings 13 and 14 may be connected respectively into line conductors'25 and 26 to load physical circuit A of loading unit X, and similarly. line windings 15 and 16, 17 and 18, 19 and 20, 21 and 22, and 23 and24, may be connected respectively into line conductors 27 and 28, 29 and 30, 31 and 32, 33 and 34, and 35 and 36, to load physical circuits B, C, D, E and F. From the physical circuits A and B may be derived the phantom circuit G, while from physical circuits C and D, and E and F may be derived respectively phantom circuits H and I.

The effect of the working of any circuit upon the other circuits through the same loading device will'now be considered and can be most easily understood by reference to the instantaneous values of current in any one circuit and the flux paths in the various limbs of the loading device corresponding thereto. As will be hereinafter more fully described, the electromagnetic interference or cross-talk between the several circuits of a single loading device, (provided the limbs of the core structure are homogeneous as regards permeability,) may be reduced to a minimum by proper initial balancing of the windings, except that from one phantom circuit to another phantom, and from a physical circuit of one unit to either physical circuit of another unit. These conditions will be apparent from a further examination of Fig. 1.

For purposes of description, it will be assumed that physical circuit A is the exciting circuit or the one over which conversation is being carried on Aand it is desired to determine what etl'ect such working will have upon the remaining circuits loaded at a given point by a single loading device. The instantaneous values of current in physical circuit A during the working thereof may be represented by the solid arrows adjacent to the line windings 25 and 26, while the direction of the flux in the'various limbs of the magnetic structure corresponding thereto may be represented by the solid arrows adjacent to said limbs. The voltage generated in the remaining line windings, tending to force currents through the other line conductors, -and the direction which such currents would assume, are shown by the solid feathered arrows adjacent to the line conductors 29 to 36 inclusive. No voltages whatever would be induced in line windings 15 and 1G tending` to cause current to flow in line conductors 27 and 28, since there is no flux in limbs 3 and 4, due to the symmetry of the magnetic structure. solid feathered arrows. there would be a flow of current in physical circuits C, D, E and F which could be heard in the connected subscribers telephones. rl`he method of neutralizing these induced currents in the complete system will be described later in connection with Fig. 2.

Looking now at the etl'ect of the working of any phantom circuit upon the other cir- As shown by the cuits loaded at a given point by means of a single loading device, it will be assumed that 'G is the exciting circuit or the one upon which conversation is being conducted. The direction of the instantaneous values of current in this circuit may be represented by the dotted arrows adjacent to line conductors 25 to 28 inclusive, while the corresponding directions ojf the tluxes in the magnetic structure may be represented bythe dotted arrows adjacent to the various limbs thereof. The voltages induced in the other line windings tending to '.ause current to flow in the other line conductors, and the directions of such current iow, are shown by the dotted feathered arrows adjacent to line windings 2 9 to 3G inclusive. From the. direction of these arrows it is seen that the currents which would be set up, could not be heard in the subscribers instruments connected to the several physical circuits, but that they could be detached 'in the-subscribers instruments associated with phantom circuits H and I. It is also seen that no voltages are induced in line windings 13 to 1G inclusive, tending to cause currents to flow in physical circuits A and B, which could be detected' by the subscribers` instruments connected to those circuits. The method of neutralizing the induced currents in phantom circuits H and l will also be described in connect-ion with Fig. 2.

In Fig. 2 are shown four loading devices connected' at four successive loading points in the line conductors 25 to 3G inclusive. As hereinbefore explained the twelve line conductors are so 0frouped as to form three loading units, X,'1 and Z. The meaning of the arrows in this figure are the same as those of Fig. 1, the solid arrows adjacent to line conductors 25 and 26 indicating the instantaneous direction of the exciting current in physical circuit A; while the dotted arrows show the instantaneous direction of current in phantom' circuit G. The feathered arrows,both solid and dotted,show respectively the corresponding induced currents in the remaining line windings 29 to 36 inclusive.

'At loading point No. 1 the line windings of device No. 1 are connected into the line conductors 25 to 3G inclusive in the identical manner shown in Fig. 1. At loading point No. 2 the windings of device No. 2 which are connected into line conductors 25 to 28 inclusive are each reversed. rI`he remaining windings of that device are connected into the remaining line conductors in the same order as those of combination No. 1. At loading point No. 3. the line windings of device No. 3 which are inserted into the line conductors 29 to 32 are reversed; while at loading point o. 4 the line windings ot' device o. i which are connected into line conductors 33 to 3G are reversed. t loading induced voltage in loading device No. 1 is opposed to the induced voltage in loading device No. 2, while the induced voltage in loading device No. 3 is opposed to that in loading device N 0.4 and, since the values of these induced voltages are all the same due to symmetrical construction of each loading device and similarity and equality between the different` devices, these induced voltages entirely neutralize each other both in direc tion and magnitude. The same is true for each of the other windings.

While the method of eliminating electromagnetic interference or cross-talk between the various circuits has been described in connection with only one exciting side circuit and one exciting phantom circuit, it is clear that the resultl would be the same regardless of which circuit, either physical lor phantom, was theexciting circuit or the one being worked.

While in Fig. 2 the loading devices are` shown at separate loading points, the tour devices may be grouped at a single loading point. Which method is to be employed in an actual installation will be dictated by the considerationsv of expediency and economy.

The principal advantage of a loading sys'- tem, as hereinbefore described, results from the economy in the use of core material.- This economy arises from the multiple use of a single core structure to load a large number of telephone circuits, which in this case is six side circuits and the three corresponding deryed phantomcircuits. While it is necessaryI in order to reduce the crosstalk between the several circuits to use these loading devices in groups of four in each, either immediately at a loading point or distributed relatively closely together in the vicinity ofthe loading points, the inductance required to be inserted at a given loading point will be split up into four equal parts, so that the size of the core structures will be correspondingly reduced and the economy in the use of core material stillobtained.

What is claimed is:

1. A unitary loading device, for more ,than two physical circuits, comprising a twelvelimbed magnetic circuit and a winding on each limb of said magnetic circuit.

2. A unitary loading device, for more than two physical circuits, comprising a magnetic circuit having twelve limbs arranged to outline a cube and a winding on each limb of said magnetic circuit'.

3. In combination with more than two physical circuits, a unitary loading device therefor comprising a twelve-'limbed magnetic circuit and a winding on each limbof said magnetic circuit said windings being connected in said physical circuits.

- 4. In combination with a plurality of line conductors arranged to form more than two physical circuits, a unitary loading devicetherefor comprising a twelve-.limbed magnetic circuit and a winding on each limb 'of said. magnetic circuit,eac,h of said wind-- ings forming a part of one of said line conductors.

5. In combination with a plurality of line conductors arranged in pairs to form physical circuits, a loading device comprising a twelve-limbed magnetic circuit outliningpthe form of a body having six faces and a winding'on each limb of said mag,- netic circuit, each of said windings forming a part of one of said line conductors and the windings for the two conductors Vvforming each physical circuit being on diagonally qpposite limbs. y

6. n combination with a plurality of physical circuits and a plurality'of phantom circuits derived therefrom, a unitary loading device therefor comprising a twelvelimbednmagnetic circuit and a winding on veach limbof said magnetic circuit, said windings being connected in said physical and phantom circuits.

7 n combination with a plurality of line conductors arranged in pairs to form a plu- ,rality of physical circuits and a plurality of phantom circuits derived therefrom, a loading device comprising a core consisting of twelve limbs arranged to outline a cube and a winding on each limb of saidcore, each of said windings forming va part of .one of said line conductors, the windings for the' two conductors of each physical circuit being on diagonally oppositelimbs and the windin s for the conductors of each phantom circuit being on parallel limbs of the core.

8. In combination with a plurality of line conductors arranged to form a plurality of derived phantom circuits, a unitary loading device therefor comprising a twelve-limbed magnetic circuit and a winding on each limb of said magnetic circuit, said windings forming partsiof said line conductors.

i 9. In combination with line conductors ar. ranged to form a plurality of derived phantom circuits, a loading device comprisin a magnetic structure consisting of a lurality of limbs arranged in groups of our, the limbs of each group beingconnected by the limbs of the other groups to form complete magnetic circuits, and a'winding on each limb, the windings oli` the limbs of each' group comprising the windings for one of.

the phantom circuits.

10. In combination with twelve line coni of said magnetic circuit, eachof said wind. .ings formlng a part of one of said line conductors.

11. In combination, a plurality of groups of linel conductors each formin a pair'of physical circuits and a derived p antom cir'- cuit, a series of loading devices each comprising a group of windings forming part of each group of line conductors; the relative direction, through each of said loading devices, of two groups ofconductors being the reverse of the relative direction of said groups through another of said loading devlces.

12. In combination, a pluralityof groups of line conductors-each forming a pairof physical circuits and a derived phantom circuit, afseries of loading devices each comprising a group of windings forming part of each group of line conductors, the relative direction, through each of said loading devices, of two "groups of conductors being the reverse -of the relative direction of 'said groups through another of said loading decuit, a series of loading devices, each lcomprising a group of windings for each group of'line conductors'and a single branched magnetic structure on which windings for rall of said line conductors are mounted, the

relative direction, through each of said loading devices, of two groups of -conductors being the reverse of the relative direction of said groups through another loading device. 14. The combination with a plurality of line conductors arranged to form a plurality of derived phantom circuits of a unitary loading device for said phantom circuits.

15. The combination with a plurality ofA physical circuits of a unitary loading device for more than two of said physical circuits, said device having a plurality of limbs and a Winding on each limb, said windings being connected in more than two of said physical circuits.

In witness whereof, I hereunto subscribe myname this 15th day of August A. D., 1917.

GEORGE A. KELSALL. 

